Fintail Exhaust manifold removal

[joshhol]

I've got a fairly simply procedure to do but I'm road blocked by the down pipes being fairly stuck to the exhaust manifold header pipes. All the other stuff is out of the way and the intake/exhaust combo pulls away from the head fine. Just need to separate the down pipes as there isn't enough clearance to slide manifolds off the head bolt studs.

I figure I could spray it with PB blaster and beat on the pipes with a rubber mallet to break them free, but I thought I'd check in here before I do something stupid, which is all too often.

[engatwork]

Do you have access to Kroil or something to heat it with?

[joshhol]

I can get access to both. Will try

[Idle]

I have run into this twice. Once was where with enough force and leverage the down pipe finally broke loose.

Another time a guy with a 250sl just went in there with a sawsall and cut the pipe off near the exhaust manifold. He then went on Ebay and purchased a manifold and a downpipe.

I would use that second option only as a last resort.

Please let us know what works in this situation. This problem will only become more common as our cars age.

[gmog220d]

If you can get enough heat into it you can try the old "heat and quench" method. This has worked for me getting things like rusty pins out of old VW Bus door hinges. Heat it up good and hot, if you can do that without messing up anything else in the area. Then, while it's hot, blast it with cool water. Do that a few times and the expansion and contraction will loosen up the rusty crud that's in between the pieces, allowing easier separation. You'd need a pretty hot torch, like an oxy/acetylene setup, maybe a MAPP torch.

[801mbz]

I use a floor jack on the exhaust pipes, tie the manifold to the side, lift manifolds and head off block, then lift head, and slide out of manifolds. You are pulling the head??

[joshhol]

I managed to get it off with repeated doses of PB Blaster and some precise raps with a hammer right at the joint. Then I wiggled the pipes from underneath (had already loosened the mount at the trans).

Came out pretty easily, hope I didn't rap it too hard.

Not pulling the head, going to see about getting those heat flaps to work and just clean things up.

Thanks for the suggestions! Amputation wasn't going to be employed and thankfully not needed.

[joshhol]

Here are some shots with the manifolds removed. The thought crossed my mind today to go ahead and pull the head now since I've gone this far, hmmm

The nuts on pic 3 that join the exhaust manifold to the intake manifold are on the outside of the assembly. They can only be accessed with an open ended 12mm wrench and of course they were rounding off. After lots of PB blaster, waiting and some large channel lock plyers, got them to budge.

There are corresponding nuts on the inside next to the head, but on the top of the intake manifold, instead of under the exhaust manifold. You can get a box wrench on that side but not with the valve cover in place. I didn't try with the cam cover off and trying to work around the valve assembly, much easier with the whole thing off.

[joshhol]

The manifolds settling in for a long vinegar bath.

[joshhol]

Well, it's been a while but I've been plugging away at this. The vinegar bath. . .hmm I came across this method on the Ponton site where a guy doused exhaust manifolds for 4 weeks. He said it removed rust and un-seized a stuck heat riser flap. Fortunately I only left my parts in for a week before checking. Rust was removed but it seemed like it was attacking the metals more than one would like. It seems to have dissolved some small bits that I left attached to the parts. Thank goodness it didn't affect the intake manifold but I wonder if it had a negative impact on the exhaust manifolds.

You can see serious pitting and corrosion of the sealing surfaces on the exhaust manifold. Additionally, the heat riser flap will not budge.
MBZ seems to have the front exhaust manifold available but it is upwards of $2,300. Yes, $2,300. The rear manifold is not available. Fortunately I found a set of good used ones in Germany and picked them up. All the gasket sealing surfaces look smooth and the riser flaps work. Yes, I could probably get mine to work but for now I'll keep them as spares and see what I can do to make them serviceable.

Regarding the new gasket, which side should go towards the head? The smooth side or the side with the pressed fittings? Should a sealant be applied?

I'll be calling MB soon to see which bits that I dissolved are still available and at least I got some engine mounts installed. The carbs are about done, just waiting on some dashpot bellows.
Got more to do though before a firing is attempted. With this much access in the engine bay, I'm trying to get to things now.

[joshhol]

Engine mounts were pleasantly easy. Will do the trans mount later.